Temperature Coefficients of the Work Functions of the (110) and (100) Surfaces of Tungsten Single Crystals and of Polycrystalline Tungsten Foil

A modification of the Kelvin contact potential difference technique has been used to measure the temperature coefficient of the work function of three tungsten surfaces over the temperature range from 77°–1300°K. Two of the surfaces were polished and etched single‐crystal planes having the (110) and (100) orientations, the third was a sample of polycrystalline foil. The results obtained were $$\begin{array}{cc}\mathrm{foil}& {\text{(11±1)×10}}^{\text{−5}}\hspace{0.17em}{\mathrm{eV/}}^{\circ }\mathrm{K}\\ \text{(110)}& {\text{(6.3±0.6)×10}}^{\text{−5}}\hspace{0.17em}{\mathrm{eV/}}^{\circ }\mathrm{K}\\ \text{(100)}& {\text{(9.1±0.4)×10}}^{\text{−5}}\hspace{0.17em}{\mathrm{eV/}}^{\circ }\mathrm{K}\end{array}$$ and these are in qualitative agreement with predictions based on the temperature dependence of the electron smoothing component of the surface double layer.